Rock　macrofracturing　often　involves　the　tension-shear　coexistence　mechanism　on　the　microscopic　scale.　This　paper　addresses　the　occurrence　of　tension　and　shear　mechanisms　in　rock　macro　-fracturing　process　based　on　the　self-developed　integrated　acoustic-optic-mechanics　(AOM)　multi　-physics　field　monitoring　technique.　With　this　advanced　technique,　three-point　bending　(3-p-b)　tests　with　conventional　loading　and　unconventional　loading,　as　a　control　of　the　conditions　that　produce　the　different　mechanisms,　are　first　carried　out　on　sandstone　to　establish　AOM　criteria　for　crack　nature　classifications.　By　using　the　AF-RA-based　Kernel　density　median　criterion　and　the　optical　angular　bisector　criterion,　a　coupled　analysis　of　acoustical-optical　data　for　the　distinction　of　tension-vs　shear-induced　cracks　in　two　different　flaw　configurations　under　uniaxial　compression　has　been　available.　Results　show　that　the　crack　initiation　mode　in　tension-type　rock　bridge　tests　is　dominated　by　the　tension　mechanism,　while　the　ultimate　failure　pattern　is　shear　-dominated.　Comparably,　failure　of　shear-type　rock　bridge　is　faithfully　dominated　by　the　shear　mechanism.　The　paper,　therefore,　makes　two　contributions-a　better　understanding　of　rock　fracturing　process　and　providing　a　method　of　establishing　the　simple　and　intuitive　criteria　to　justify　the　crack　natures.